The Watcher Mask is just like every other Watcher mask, except that it is dented and somewhat beaten up, which shows that it was scavenged from the battlefield. The Mask is also equipped with a radar, which allows Will to see where his enemies are on the battlefield. The radar automatically enlarges it area of effect whenever Will is flying.
At first, Will was reluctant to use the Mask because he did not want to be like his enemy. To this Atem responded that as long as he didn't let the Mask consume him, Will would not turn into one of the Watchers if he used it.
At the very end of the game, once you have destroyed two out of the three "heads/eyes" of The Dweller, he will throw you to the top of the Tower, where you will lose half of the Watcher Mask breaks off from the rest due to the sheer force of Will hitting the surface of the Tower. After he defeats The Dweller, Will throws away the last half of the Mask due to the fact that it is ruined now.